What GPS Datum do I use for walking in Spain?
Q. When I am using my etrex30 in Spain how do I change the settings for a GPS reading
Christine Acton, Altrincham
A. There are several variants of the European Datum - the best fit for Spain is "ED50 Spain and Portugal". The digital maps from CNIG are mostly WGS84 now. They are free to download and there is software that will convert them for most Smartphone apps and some GPS devices. On thing to be aware of, the maps of El Hierro use UTM zone 28 but the far west of the island is in UTM zone 27.
John Thorn, Cardiff
A. The setting you need for your my Garmin eTrex30, or any other handheld GPS device, in Spain is usually written on the edge of the map. Somewhere in the margin it will say something like 'European Datum 1950' (most likely), 'UTM UPS' and/or 'WGS 84'.
If it says 'European Datum 1950' you should go to 'Setup' on your Etrex and then 'Position Format' and set the Datum name to 'European 1950'.
Not all Garmin GPS devices have this datum. My Garmin eTrex 10 does not and as far as I am aware, nor does the Garmin eTrex 20 or the Garmin eTrex 30.
If this is the case then, regardless of waht it says on the map, you should select 'Setup' on your GPS device and then 'Position Format' and select 'UTM UPS' which will automatically load the 'WGS 84' Map Format.
With this setting you will find that the indicated GPS location on your Etrex will be about 100m east of the identical location on the map. You will just have to allow for this discrepancy when establishing your actual location.
The reason for this inaccuracy is that Spanish maps are somewhat behind the times. Until relatively recently, detailed 1:50,000 and 1:25,000 scale were only available to the military. They use the European Datum 1950 which was established just after the 2nd World War and they didn't need to be updated to fit in with the rest or Europe. While the detail on these maps is pretty good, there is little or no reliable information about local footpaths.
Hope this helps . . .